Determining the positions of remote communications devices and assets to which they may be attached is a critical challenge for which previously available solutions are increasingly inadequate. For example, when a remote communications device is in communication with a Wide Area Network (WAN) transmitter, location of the communications device on a macro scale is available by way of knowledge of both the position of the WAN transmitter and the maximum effective range of the communication.
Techniques for determining more precisely the location of an asset are available. Such techniques involve determining Time of Arrival (TOA) and Time Difference of Arrival (TDOA) of radio frequency (RF) signals to deduce distances between wireless devices. In addition, determinations of Angle of Arrival (AOA) are utilized to deduce directions of signals. Global Positioning System (GPS) technology is also available for determining, with relatively high precision, the locations of assets equipped with specialized receivers that measure time travel of radio signals from satellites. However, these known technologies are vulnerable in that electronic signal jamming technologies are capable of blocking wireless signals to deny the ability to locate assets. Accordingly, a method of determining the location of a communications device that is not susceptible to jamming technologies is needed.
Celestial navigation is a position fixing technique that was the first system devised to help sailors locate themselves on a featureless ocean. Celestial navigation uses angular measurements, i.e., sights, between the horizon and a common celestial object. The Sun is most often measured. Skilled navigators can use the Moon, planets or one of the 57 “navigational stars” that are described in nautical almanacs. Sights on the moon, planet and stars allow navigation to occur at night or when clouds obscure other objects.
Celestial navigation works because at any given instant of time, any particular celestial object will be directly over a particular geographic position on the Earth, i.e., it will have an exact latitude and longitude. The actual angle to the celestial object locates the navigator on a circle on the surface of the Earth. Every location on the circle has the same angle to the celestial object. The circle will be centered on the celestial object's latitude and longitude. Two or three sights on different objects, or at different times, establish that the navigator is at the intersection of several such circles. The sights are reduced to positions by simple methods that add and subtract logarithms of trigonometric values taken from tables.
Practical celestial navigation usually requires a chronometer to measure time, a sextant to measure the angles, an almanac giving angular schedules of celestial objects, a set of sight reduction tables to help perform the math, and a chart of the region. With sight reduction tables, the only math required is addition and subtraction. Small handheld computers and laptops enable modern navigators to “reduce” sextant sights in minutes, by automating all the calculation and data lookup steps.
Celestial navigation is not dependent on receipt of RF signals. Therefore, it would be advantageous to be able to use the basic techniques of celestial navigation to determine the location of remote communications devices.